The present invention relates to a method and apparatus for controlling parameters of a drying cycle for a clothes dryer using sensor-based fuzzy logic.
Typically in dryers known in the art, full heating energy is applied to a clothes treatment chamber throughout a drying cycle up to a point in time when a sensed moisture content of the clothes is reduced below a threshold level. At this point or a predetermined time period thereafter, the drying energy is terminated and the drum of the dryer continues to rotate for a predetermined amount of time to allow cooling of the clothes treatment chamber. When a sufficient time to allow cooling or a cool down temperature has been reached, the dryer is then shut-off. Alternatively, it is also known in the art to simply maintain an exhaust temperature of the dryer at a set temperature level after an initial period of heating from the start of the drying cycle for a predetermined time period.
Studies have shown that users of prior art dryers believe that automatic drying cycles either leave their clothes overdried or underdried. As a result, users will more frequently use timed drying cycles to guarantee dryness or, alternatively, intervene during the drying cycle to remove clothes in mid-cycle to prevent over-drying based on fear of shrinkage and fabric damage. In addition, conventional dryers set drying temperature based on a drying cycle selection and do not control the temperature based on the clothes moisture content. Typically, higher temperatures are required to heat the clothes load at the beginning of a drying cycle and consequently remove a higher percentage of the moisture from the clothes load. However, as the clothes moisture content decreases, the temperatures of the clothing fabrics can increase rapidly, thus causing possible damage to the clothes.
Moreover, conventional dryers do not estimate remaining time in a drying cycle taking into account differing load sizes and types. Thus, the estimated time can be the same whether a 3 pound load or a 15 pound load is being dried, for example.
Accordingly, given the above problems with conventional dryers there is a need for control of a dryer that better determines and indicates the dryness state of a clothes load and more accurately predicts an appropriate drying time. In addition, there is a need for estimating remaining drying time taking into account different load sizes and types.
The above needs and other needs are met by the present invention that provides a method and apparatus for controlling a dryer employing a fuzzy logic scheme that utilizes multiple sensor inputs to better determine the drying state of a clothes load and predict an appropriate drying time. In addition, a method and apparatus are provided to detect when a clothes load is in an acceptable range of dampness and alert a user of the dampness state. The method and apparatus may utilize a user""s cycle selections to provide further information on a clothes load, thus further assisting to determine an appropriate drying time for the load.
According to one aspect of the invention, a methodology is provided for controlling dryer by first selecting a first prescribed drying cycle setting prior to a start of a drying cycle. Next, moisture information within the dryer is monitored over a predetermined period of time. At least a portion of a time of the drying cycle is then set using predetermined fuzzy logic functions and rules based on the selected first prescribed drying cycle setting and at least the monitored moisture information. By utilizing fuzzy logic, the dryer cycle can be more accurately controlled by accommodating for degrees of variables present in differing clothes loads.
According to another aspect of the present invention, an apparatus for controlling a dryer is provided for a dryer utilizing fuzzy logic for a controlling a dryer includes a user interface for receiving a drying cycle selection from a user. At least one moisture sensor is provided for sensing moisture level of a clothes load in the dryer. A controller receives inputs from the user interface and the at least one moisture sensor and includes a fuzzy logic control portion. The controller is configured to determine one or more time dependent parameters based on information input from the at least one moisture sensor and input the one or more parameters to the fuzzy logic control portion. The fuzzy logic control portion within the controller is configured to calculate fuzzy logic rules that determine drying cycle modification information based on predetermined fuzzy logic functions within the fuzzy logic portion. Also, the fuzzy logic control portion determines clothes load characteristics based on the one or more parameters. The fuzzy logic control portion is further configured to output the drying cycle modification information to the controller, which modifies the drying cycle in accordance with the drying cycle modification information.
Additional advantages and novel features of the invention will be set forth, in part, in the description that follows and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.